In order to extract, from a three-dimensional image captured by CT (Computed Tomography), MRI (Magnetic Resonance Imaging), a confocal laser microscopy, or the like, various pieces of information (a shape, a volume, a topology, etc.) concerning an object to be observed such as an organ or a bone structure, it is necessary to extract, from the three-dimensional image, a region which corresponds to the object to be observed. Against a backdrop of this, various methods for automatically extracting, from an image, a region which corresponds to an object to be observed have been developed. However, a region automatically extracted from an image does not necessarily accurately represent a shape of an object to be observed. This requires correcting a region automatically extracted from an image while visually inspecting the image, so as to approximate, with high accuracy, a shape of an object to be observed.
Examples of a method for supporting such a correction include a contour correcting method described in Patent Literature 1 and a region correcting method described in Patent Literature 2. The contour correcting method described in Patent Literature 1 is directed to edit, by simple operation, a contour generated from a two-dimensional image by auto tracing. The region correcting method described in Patent Literature 2 is directed to simply and easily correct, by use of a guide region, a missing part or the like of a region extracted from a three-dimensional image.